The video tape editing control system of the invention fulfills a growing need in the television industry for a practical means to permit accurate and rapid editing or video tapes, so that a finished edited master tape may be produced from the video information on one or more original tapes, or directly from a video camera. A system is described in U.S. Pat. No. 4,040,098 which is assigned to the present Assignee, which fulfills the aforesaid need in that it provides a low cost and accurate control system which is capable of interfacing both the cassette and open reel types of helical scan video tape recorders for precise tape-to-tape or camera-to-tape editing. The system of the present invention presents simplifications and improvements in the joystick control; and it also presents simplifications in circuitry and reductions in cost, in that it is microprocessor controlled. Moreover, the system of the present invention is modular in form so as to be adaptable from a basic unit to more complex configurations, as mentioned above, and as will be described in detail in the present specification.
It is conventional practice to provide video tapes with a control track in which pulses are recorded at pre-selected rate for control purposes. The editing control system of the invention utilizes the pulses from the video tape control track precisely to control the operation of both the source video tape recorder and the record video tape recorder around the selected edit frame, thereby obviating the need for complicated time codes on the tapes themselves, and for ancillary complex control equipment.
The editing control system of the invention, in the embodiment to be described, includes a single manually-operated joystick potentiometer means which serves to control the forward and reverse movements of the video tapes in the source and record video tape recorders in the vicinity of the edit frames so as to permit exact edit frames on the tapes to be selected. The joystick provides an extremely tight control of tape speeds in either direction from still frame up to, for example, three times normal tape speed. A "cruise" control switch is also provided to enable the tapes to be driven indefinitely at any set joystick speed.
The editing system of the invention, similar to the editing system illustrated and described in the aforesaid patent, and as will be described, may use a single cathode-ray tube monitor, which monitors both the source and the record video tape recorders, and which may be controlled to provide a repeatable preview of the individual edit frames before an actual "edit" or transfer of information to the record video tape recorder is made.
In the editing control system of the invention, as in the system disclosed in the aforesaid patent, the video signals are fed directly from the source video tape recorder to the record video tape recorder. It is, therefore, possible to use time base correctors, processing amplifiers, drop-out compensators, or the like, without affecting in any way the operation of the editing control system. Also, since the editing control system does not process any of the video signals themselves, the quality of the video signals is unaffected by the control system.